Linear actuator is used extensively in many areas and installed to electric hospital beds, treadmills, wheelchairs, etc for adjusting a position, a height, and an angle of elevation. In particular, a quick release mechanism is provided for releasing the actuator quickly in the process of treating a patient in an emergency situation, so that the bed can be adjusted quickly to strive to earn the most precious recue time. However, the patient may be injured by the impact produced by a rapid drop of the bed. Therefore, it is a main subject of the present invention to provide a buffer effect for the rapid drop of the bed.
In general, a conventional linear actuator comprises a motor, a transmission mechanism and a quick release mechanism, wherein the motor includes a worm, and the transmission mechanism includes a lead screw and a worm gear sheathed and coupled to the lead screw and engaged and transmitted with the worm, and the quick release mechanism includes two cylindrical coupling members, and one of the cylindrical coupling members is fixed and coupled to the lead screw and rotated with the lead screw, and the other cylindrical coupling member is fixed and coupled to the worm gear and rotated with the worm gear, and a torque transmission element is installed at a corresponding end of each cylindrical coupling member, and the clutch effect between the cylindrical coupling members is provided for the transmission of the lead screw and the worm gear or releasing the transmission.
However, the actual applications of the conventional linear actuator still have the following problems. In the conventional linear actuator, a pneumatic rod is generally installed next to the linear actuator to provide the buffer function, but the additionally installed pneumatic rod incurs a more complicated structure and a higher manufacturing cost of the bed. In addition, the impact force produced by the gravitational acceleration is usually much greater than the maximum load bearable by the pneumatic rod, and thus not just damaging the pneumatic rod only, but also failing to protect the patient comprehensively. Obviously, the conventional linear actuator requires improvements.